Why have they assumed she will 'kick off'? Has the same letter been sent to all of the employees or just your wife?
It may be that they've already made their decision and are planning to make your wife redundant, as opposed to another staff member. Is your wife quite outspoken or confrontational? Perhaps they expect her to raise some of the points you have. Hard working staff, unfortunately, aren't always the favourites.
If I was your wife and I felt they had already made their decision (and unfair at that), I would 'kick off' anyway. Sure, I'd have ten minutes to pack up my stuff but I'd be prepared for that to happen and if my contract said they'd have to give me 4 weeks notice (for example), they still have to pay me for that notice period. If you genuinely feel as though her employers are being unfair - don't let her give them an easy ride.